Choice under Partial Uncertainty

This paper analyzes problems of choice under uncertainty where a decisionmaker does not use subjective probabilities. The decisionmaker has a set of beliefs about which states are more likely than others, but his beliefs cannot be represented as subjective probabilities. Three main kinds of decision rules are possible in this framework. These are maximin-type, maximax-type, and choosing that action that gives the highest payoff in the state, which the decisionmaker believes to be most likely. The author replaces the commonly used 'merger of states' axiom with a version of the sure-thing principle.